Oxygen is an essential element for the life of all aerobic organisms. However, since oxygen is metabolized in animal tissues by subsequent reductions to superoxide anion, hydrogen peroxide and hydroxyl radical, these metabolites represent a potential threat to the living organisms themselves. These different metabolites are known as reactive oxygen species (ROS).
At low concentrations, the ROS play essential intracellular functions acting, for example, as second messengers, gene regulators, and mediators of cellular activation (kinases and transcription factors). They also play a key role in the defense against infectious agents and they are modulators in the process of cell death, both apoptosis and necrosis.
When ROS levels are high and the cellular systems are no longer able to eliminate them, an imbalance between ROS and antioxidants occurs that is known as oxidative stress.
The oxidative stress is detrimental both for the cells and for the extracellular matrix, the nuclear and mitochondrial DNA, the membrane lipids, and the proteins.
Specifically, the DNA damage (single-stranded lesions, bases deletions, or “cross-linking” between DNA and proteins) forms the basis for UV-induced skin carcinogenesis, while the lipid peroxidation affects the phospholipids both from a structural and a functional point of view, thus leading to rigidity and permeability of cell membranes.
Changes at the protein level, both direct and activated by proteases, are reflected on the skin as an alteration of collagen and elastin.
Furthermore, the excessive production of ROS can induce mitochondrial damage, leading to a sharp reduction of ATP and cell death due to necrosis.
The skin is constantly influenced by environmental factors and, specifically, by UV rays. In the skin, the free radicals produced by UV radiation can cause damage to the cellular structures (DNA, proteins) and destabilize the keratinocytes membranes, resulting in premature aging of skin cells.
Particularly when exposed to UV radiation, the skin undergoes alterations resulting in inflammatory phenomenons, photo-aging, and skin diseases.
Photo-aging is accompanied by the appearance of wrinkles, loss of elasticity, increased fragility of the skin and a slower healing process.
In order to avoid ROS induced damage, by maintaining the balance in their production, the tissues are equipped with antioxidant systems that inhibit ROS production through a direct “scavenging”, decrease the amount of oxidizing agents inside and outside the cells, prevent ROS from reaching their biological targets, limit the propagation of oxidizing agents as occurs during lipid peroxidation, and counteract the oxidative stress thereby preventing aging.
In WO2011/132177 the same Applicant describes the use of 2,4,6-octatrienoic acid, and some derivatives thereof, as endowed with a remarkable antioxidant activity measured in tests of inhibition of LPS-induced ROS and in tests of lipid peroxidation induced by TBT, using Trolox, a known derivative of vitamin E, as a positive control.